Field of the Invention
The present invention relates to a photoacoustic microscope and a photoacoustic signal detection method.
Description of the Related Art
Photoacoustic waves are one kind of elastic waves generated in the process of thermoelastic phenomenon caused when a substance is irradiated with light having an absorption wavelength band. Photoacoustic imaging is thus drawing attention as a method for imaging absorption characteristics.
A photoacoustic microscope, which applies photoacoustic waves to a detection signal for imaging, employs a method involving using pulse light adjusted to an absorption wavelength band of an object to be observed as excitation light, focusing the excitation light by an objective lens to scan the inside of a sample with a focused spot, and detecting photoacoustic waves generated at each focused spot position by a transducer or other such devices.
An example of the configuration of the photoacoustic microscope configured to acquire a super-resolved image is proposed in J. Yao, L. Wang, C. Li, C. Zhang, and L. V. Wang, “Photoimprint Photoacoustic Microscopy for Three-Dimensional Label-Free Subdiffraction Imaging,” Physical Review Letters 112(1), 014302 (January 2014). The proposed photoacoustic microscope photographs the same place twice. A sample is first photographed such that an area around the center of an optical spot is bleached more than the vicinity of the optical spot. Measuring the same place once again and determining a signal difference enables the diameter of the spot bleached by the first photographing to be acquired. As a result, a super-resolved image can be acquired.